Description: Cataract disease, the leading cause of blindness worldwide, is the end result of increased scattering of light within the human ocular lens. The proposed research aims to examine the molecular origins of age-related increased light scattering in the human lens. Static and quasielastic light scattering will be used: First. to quantitate the light scattered from the mobile and immobile scattering sources in the intact, normal human lens in vitro as functions of age. Second, to examine the role of protein interactions in producing the light scattered from the young human lens. Third, to develop a concentrated in vitro lens protein model system containing protein aggregates as well as interprotein interactions, as in the ocular lens cytoplasm, and examine the relevant principles governing static and quasielastic light scattering. Fourth, to study the kinetics of lens protein aggregation in both dilute solutions and in concentrated solutions in which interprotein interactions substantially mediate the kinetics.